1. Field of the Invention
The present invention relates to an improved device for mounting and dismounting a chain block to and from a suspension ring, said device being designed so that the hook of a chain block can be mounted and dismounted to and from a suspension ring held at a high place as by a load suspending tripod or a suspension ring connected to a support member at a high place inside or outside a building, easily, safely and positively by an operation from the ground.
2. Description of the Prior Art
For mounting and dismounting a chain block to and from the head of a load handling tripod, it has heretofore been common practice to tie one end of a single rope to the linking hook (hereinafter referred to simply as hook) of the chain block while passing the other end of the rope around a horizontal pin which connects a suspension ring to the lower surface of the head of the tripod, and to pull the other end of the rope downwardly to pull up the chain block so as to engage the hook of said chain block with said suspension ring.
With this method, however, since a single rope is used for pulling up, the twist in the rope affects the lifting operation such that the opening in the hook of the chain block does not always face to the suspension ring. Therefore, it is necessary that the chain block lifted to the high place be manually changed in direction to adjust the direction of the opening in the hook. This operation is difficult and entails danger particularly where the suspension ring is located at a high place which is far above the height of a man; thus, a joint operation of two or more persons is required. For dismounting, the rope is quickly and strongly pulled to cause quick ascent of the hook, with the lower edge of the opening in the hook outwardly kicking the suspension ring, the rope being then slackened by making use of an instant which precedes the restoration of the suspension ring to its original position, thereby disengaging the hook of the chain block from the suspension ring. In cases where the chain block is heavy or said instantaneous disengagement is not smoothly effected, however, the total weight of the chain block and hook is suddenly imposed on the tension rope portions, thus entailing danger on the operator while requiring high physical force and skill on the part of the operator. Further, since a violent tension is often applied to the rope in cases where a heavy chain block is pulled up or down by the rope tied at one end thereof to the hook of said chain block, the knot in the rope sometimes loosens, possibly leading to a free fall of the chain block.